Process and apparatus for recovering and processing by-products at a coal distillation plant



l ,9 79,046 NG 2 Sheets-Sheet l LLATION PLANT 1929 FOR RECOVERING ANDPROCESSI S. P. MILLER TUS Filed-June 14,

BY-PRODUCTS AT A COAL DISTI PROCESS AND APPARA NMR Oct. 30, 1934.

N ENTO i mz. 2

ATTORNEYS S. P. MILLER TUS Oct. 30, 1934.

1,979 AND PROCESSI non PLANT PROCESS AND APPARA FOR RECOVERING NGBY-PRODUCTS AT A COAL DISTILZL Filed June 14, 1929 2 Sheets-Sheet 2kwwtw tau INVENTOR W' 24% BY gwwrh A1TORNEY5 Patented Oct. 30, 1934' TESifiiid PATENT OFFICE PROCESS AND APPARATUS FOR RECOVER- ING ANDPROCESSING BY-PRODUCTS AT A COAL DISTILLAT ION PLANT Stuart ParmeleeMiller, Englewood, N. J assignor to The Barre N. Y., a corporation ttCompany, New York,

o i' New Jersey Application June 14, 1929, Serial No. 370,954

7 Claims.

This invention relates to the recovering and processing of by-productsat a coal distillation plant, such as a coke oven plant. It includesboth the process and apparatus for carrying it out.

According to the usual operation of a coke oven battery, the gasesleaving the ovens are collected in a gas-collector main and partiallycooled therein. The cooling of the gases causes higher boiling resins orpitches and oils to separate from the gases together with a portion ofthe entrained solid impurities carried from the ovens by the gases.These ingredients constitute a heavy tar. After leaving the collectormain the partially cooled gases are further cooled and a tarry oilseparates, which comprises oils of lower boiling range and at least aportion of the impurities remaining in the gases. This product is hereinreferred to as a light tar or tarry oil. The heavy tar from thecollector main is a heavier product than the tarry oil and contains oilsof higher boiling range and a lower. proportion of oils of lower boilingrange. The tarry oil is relatively rich in tar acids and ordinarily hasa relatively high naphthalene content. It is customary to blend theheavy tar and tarry oil and where clean oil distillates are desired, thetotal tar thus produced is ordinarily shipped to a tar distillationplant'to be distilled.

According to this invention the hot coal distil- 30 lationgases from acoal distillation plant are fractionally cooled to separate tarfractions comprising oils of different boiling ranges, and thesedifferent tar fractions are differently treated. The heavy tar from thecollector main of a coke -oven plant and the tarry oils from thecondensers, for example, may be separately collected and not blended, asin the usual methods of procedure, but separately and differentlytreated. According to the invention. a heavy tar fraction such as theheavy tar from the collector main is distilled. The distillation iscontrolled so as to produce a desired oil product or a desired pitch,either of which may be used directly or after blending with tar such asthe light tar or tarry oil from the condensers.

The heavy tar. predominates in higher boiling oils and has a relativelylower percentage of oils of lower boiling range as compared with thetarry oil from the condensers or the total tar produced by blending thevarious tar fractions in accordance with the usual practice. Ondistilling the heavy tar a distillate comprising oils of relativelyhigher boiling range will be obtained and this distillate will have arelatively low tar acid content and will be relatively poor innaphthalene. Clean oil distillates of higher and lower boiling range maybe obtained by fractionally recovering the distillate from'the heavytar. The clean oil of higher boiling range will have a still lowercontent of tar acid and also less naphthalene. On the other hand, theclean oil distillate of lower boiling range will if well fractionatedcontain more naphthalene and may be relatively rich in tar acids. Thedistillate, preferably the lower boiling distillate fraction, may beextracted to recover tar acids. The resulting neutral oil may be used inpreparing creosoting composition or it may be blended with pitchresulting from the distillation oi the tar and burned for fuel. Whereonly the lower boiling fraction of distillate is extracted for taracids, the neutral oil obtained may be blended with thehigher boilingdistillate fraction and the blended mixtureused as clean creosote oil.The preparation of clean creosote oil in this manner is particularlyapplicable to the treatment of distillate resulting from thedistillation of the heavy tar to a high melting point pitch, forexample. pitch with a melting point of 350 or 400 F. Where constituentsof high boiling point are distilled from the tar and it is desirable toblend these, with oils of lower boiling range in preparing an oilsuitable for creosoting, the neutral oil above referred to may be usedas the oil of lower boiling range.

For some purposes tar products containing a small amount of free carbonmay be desirable. In the manufacture of creosoting compositions of theso-called coal tar solution type, for example, a small amount of freecarbon, for example, up to 2 or 3% of free carbon, is permissible.According to this invention, the distillate from the heavy tar may beblended with other heavy tar or with tarry oil or total tar to producecreosoting com.

position. Creosoting composition is ordinarily prepared by blending acertain amount of distillate from total tar with a small amount of totaltar, for example. 80% of distillate may be blended with 20% of totaltar. Accordingto the method of this invention, the heavy tar distillatemay be blended with tarry oil to produce creosoting composition. Owingtothe fact that the tarry oil contains a smaller percent of free carbonand predominates in oils of lower boiling range than ordinary total tar,a larger percentage of tarry oil may be blended with the distillate toproduce creosoting composition than the per centage of total tarordinarily employed for blending.

The heavy tar may be distilled to pitch of highe er or lower meltingpoint. When creosoting comiimite thereto.

position is to be prepared from the distillate and oils of higherboiling range are desired in the creosoting composition, a pitch oi highmelting point, e. g. in the neighborhood of 350 F. or over, will beprepared in order to throw oils of higher boiling range over into thedistillate. The pitch produced may be utilized as such, for example as abriquette pitch, when the melting point is approximately 185 F. or thepitch may be blended with heavy tar or tarry oil or total tar fromanother plant and be used as fuel.

A pitch of a high melting point or relatively high melting point mayreadily be blended with the tar by mixing the pitch with the tar whilehot. A stream of the tar and hot pitch from sep arate' nozzles may bedirected toward one another on entering a mixing tank in such a way thatbefore the streams of pitch and tar reach the blended mixture in themixing tank, considerable has taken place. By heating the tank asfwithsteam; coils, and agitating the tar and pitch within the tank,wherenecessary, and also heating the tar where necessary, a homogeneousmixture well suited for use as iuel may be obtained. By regulating thetemperature, a thinly fluid fuel may be produced. It may be desirable toenclose the mixing chamber and equip it with a refi ux condenser toprevent the escape of oil vapors to the atmosphere.

The method of this inverition may readily be carried out at an ordinarycoke oven plant without extensive alteration oi (the by-product recoverysystem, The invention may, for example, be carried on, in connectionwith a Semet-Solvay plant, or at a K oppers plant by providing separatemeans tor the recovery of heavy tar and tarry oil, {and means fordistilling the heavy tar.

The invention will be gturther described in connectiohwith theaccompanying drawings, but it is into ded ahd is to be understood thatit is not In t e drawings- Fig. 1 is azplan view of apparatus forcarrying out the invention;

2 is elevation apparatus o Fig/:1; and

Fig. 3 is a] section of the still taken on line 3-3 of Fig. 2. I

The battery of coke ovens 5 is provided with a collector main 6 whichconnects with each 0! the ovens fthru uptake pipes and goose-necks 7. Across-over main 8 connects with the condensers 9 and lO and an exhauster11 is provided for drawing the gases thru the system.

Where the battery is of the Semet-Solvay type in which /the gases aresprayed with ammonia liquor in the collector main, means for sprayingpartly in section of the the gases in the ;collector main are providedand the gases may also be sprayed in the goose-necks. The gases arethereby cooled and the heavy oils separated from the gases carry withthem entrained impurities. The heavy tar thus produced is withdrawn fromthe collector main together with unvolatilized ammonia liquor into thedecanter 12. Heavy tar is separated into the tank 13.

According to a common method of operating a coke oven battery of theKoppers type, tar and ammonia liquor which separate from the collectormain and tar and ammonia liquor from the condensers are collected in acommon storage tank and a mixture of this tar and ammonia liquor iscirculated thru the collector main. This cools the gases in thecollector main and higher boiling oils separate from the gasesdissolving in the tar 'and carrying with them entrained impurities.

The heavy tar from the collector main and tarry oil from the condensersare not ordinarily collected separately. The present invention, however,contemplates separate collection of heavy and light tars and theoperation of the collector main must be modified to meet theseconditions.

Where the invention is carried out at a plant comprising ovens connectedwith more than one collector main, a mixture of the tar and the tarryoil from one or more other collector mains and condensers may be usedfor flushing the collector main 6 to prevent the accumulation of pitchtherein. This flushing of the main will cool the gases, and cause theseparation of heavier oils from the gases. A heavy tar will in whichwill predominate in higher boiling constituents which separate from thegases in the collector main. A portion of this tar may be recirculatedthru the collector main. The balance may be kept separate from the tarryoil separated in the condensers. It may be run to a storage tank, suchas 13, for further treatment.

Where the ovens connected with the collector main 6 are to be operatedas a separate unit, 1. e. where the gases in the collector main are notto be cooled with tar and ammonia liquor derived from the gases fromother coke ovens, the heavy tar which separates in the collector mainmay be recirculated thru the collector main to flush the main and tocool the gases and condense heavier oils to produce further heavy tar.Instead of recirculating heavy tar from the collector main back thru thecollector main alone, it may be blended with tarry oil or ammonia liquorand tarry oil from the condensers and the blended mixture may then beemployed for flushing the main and cooling the gases in the collectormain to separate the heavy oils therefrom.

Tar from another source, house tar, or even water gas tar, may besupplied to the collector main 6 and caused to flow thru the main toprevent the accumulation oi deposits of pitch, and a portion of theheavy tar drawn off from the collector main may be recirculated withthis tar. Where the main is operated at high temperatures, as where noammonia liquor is supplied to the main, or where the amount of ammonialiquor is limited, there may be some distillation of tar within themain.

Where tar or tar ammonia liquor are circulated merely thru the bottom ofthe main to prevent the accumulation of pitch deposits, the gases may besprayed at least to some extent with ammonia liquor to cool the gasesandseparate oils therefrom and such cooling may be regulated to providefor controlling the amount and character of the tar recovered from themain.

The cooling in the collector main may be regulated to control theboiling range of the oils condensed in the collector main. Suchregulation simultaneously controls the boiling range of the tarry oilscondensed in the condensers. By reducing the amount of ammonia liquorsprayed into the gases in the collector main-tor example, the reductionin the temperature of the gases in the collector main will be less andconsequently the gases will leave the main at a higher temperature andwill carry with them a higher percentage of oils, especially oils ofhigher boiling range. On cooling these gases a heavy tarry oil will beobtained from the condensers and this tarry oil will contain arelatively high percent of oils of high boiling range. On the otherhand, by increasing the extent to which the gases are cooled in thewhich may be gas- .of the still so that the collector main. a tar willbe obtained from the collector main which will contain a higherpercentage of lower boiling oils, and the tarry oils from the condenserswill comprise oils of relatively lower boiling range than usual. Bycombined control of the'cooling to which the gases are subjected in thecollector main and the subsequent. distillation of the heavy tar fromthe collector main, various distillate oils and pitches may be producedfrom this heavy tar.

Various types of stills may be employed for distilling the heavy ar. Apipe coil still may be utilized in which the tar is heated and theheated tar may then be passed to a vapor box in which vapors resultingfrom the heating of the tar separate from the residue. On cooling thevapors a clean oil distillate will be obtained. Vacuum may be employedon the vapor chamber. to aid in the distillation.

According to the preferred method of carrying out the invention, theheavy tar is distilled by bringing it into direct contact with hot cokeoven gases or by combined direct and indirect contact as disclosedbelow.

The still 20 is preferably located at the side of the coke oven batteryopposite the usual collection oven. Hot gases from selected ovens of thebattery pass thru the uptake pipes and goosenecks 21 into the header 22.By the proper manipulation of valves in the uptake pipes and goosenecks7 and 2-1, the gases from the ovens connected with the hot gas header 22may be diverted either to the collector main 6 or to this header 22. Thegases passing thru the uptake pipes 21 and hot gas header 22 into thestill 20 are brought into direct contact with an intense spray of tarwithin thestill 20.

The still is provided with agitating means. This comprises the roll 23which is located at one side of the still and so situated that it dipsto a slight extent into a body of the tar or partly distilled tar whichis maintained in the bottom of the still. The roll is adapted to berotated at a speed of 9001200 R. P. M. by the motor 24. The tar to bedistilled may be fed to the still thru the pipe 25 or preferably thruthe pipe 26 which leads into the tower 27 thru which the gases andvapors leave the still. The tar sprayed into the tower thru pipe 26 inpassing down thru the tower in direct contact with the gases and .vaporsis heated and caused to approach equilibrium with the rising gases.Battles 29 are provided below the nozzle 30 in order to expose a largesurface of the tar to the action of the gases and thus to facilitateheat exchange between the gases and the tar. Barnes 28 may be providedabove the nozzle 30 to assist in removing entrained material from thegases. The tar which collects in the bottom of the tower is preferablydrawn 011 thru the pipe 31 and admitted to the still at the opposite endtar and the gases pass thru the still in concurrent direction, the gasinlet at the bottom of the tower being so designed as to preventdownward flow of tar thru it into the still. Where pitch of high meltingpoint, e. g. pitch with a. melting point in the neighborhood of 350 or400 F. is to be produced, this concurrent flow of tar and gases isdesirable. Where lower melting point pitch is to be produced,countercurrent flow of tar and pitch may be used. In such a case tarsprayed into the tower may drain down into the still thru the gasconnection between the still and the tower, and the pitch outlet willthen be situated at the opposite end of the still.

The pitch produced is withdrawn from the still thru the tar trap 32 andthe levelling arm 33. By regulating the position of the levelling arm,the amount of partially distilled tar or pitch retained in the still maybe controlled and thus the extent to which the roll 23 dips into thepitch is regulated. The pitch may be granulated by chilling with coldwater, or it may be flaked, or treated in any desired manner. It may bedrawn oil into the mixing tank 34 and mixed with tar for fuel or toproduce pitches or for other purposes.

The tar for blending with the pitch is supplied thru the line 35. It maybe tarry oil from the condensers or heavy tar from the collector main,or tar from other sources. The tar from 35 and pitch from 33 enter thetank in such a way that after they leave the lines thru which they areconveyed to the tank and before they reach the level of blended materialwithin the tank, they are mixed to a considerable extent as they fallinto the tank. The tank may be provided with agitating means. A steamcoil 37 is shown for use when required to maintain the contents of thetank 34 in a thinly fluid and homogeneous condition. The levelling arm33 and tank 34, etc.

may advantageously be enclosed and a reflux denser 38 provided. Anycondensate from condenser may be returned to the tank 34, or covered asa separate product.

Heavy tar is distilled in the still. the tank 13 may be pumped directlyinto the still or it may advantageously be brought into indirect contactwith the hot gases and vapors leaving the still before being broughtinto direct contact with the gases in the still. In the former inlet atthe bottom of the tower is so designed as to allow any reflux formed inthe tower to reflux into the still. The gases and vapors leave the stillthru the tower 27 and the main 40. They pass conthe

The tar from case the gas thru the heat interchanger 41, thru the main42 into the condenser 43, and thence to an exhauster,

which may be the exhauster 11. p

According to the preferred method of operation,

heavy tar from the collector main is pumped from the tank 13 by the pump44 thru the line 45 into 20 the pipe coil 46 within the heatinterchanger 41. The gases and vapors within the heat interchanger arecooled and a clean oil of relatively,

high boiling range is drawn off from this heat interchanger into thetank 47. The tar heated in the heat interchanger is passed thru the line48 into the vapor chamber 49 where partial distillation occurs. Thevapors are drawn oiT thru the main 50 into the condenser 51 where cleanoils of relatively low boiling range are condensed separately collectedin the tank 52. The pitch residue is fed to the still preferably thruthe tower 27 by means of the pump 53', the line 26 and the nozzle 30.

and

The tar is fed from the bottom of the tower thru the line 31 into thestill 20 and is there brought into direct contact with the hot gasescoming from the hot gas header 22. The spray of tar thrown up into thegases by the roll 23 is so intense that the stantially de-tarred, i. e..entrained impurities are removed from the gases so that the gases andvapors leaving the still thru the tower 27 are substantially free fromentrained impurities. These gases and vapors where heavier oils areseparated and then to the condenser 43 where the remaining oils separatefrom the gases and are collected in the tank 53.

By first distilling the tar by indirect contact gases are scrubbed andsubpass to the heat interchanger 41 with the hot gases and vapors beforebringing it into direct contact with the gases, the lighter oils aredistilled from the tar and separately collected and the hot gasespassing thru the still are enriched only in higher boiling constituents.These 5 higher boiling constituents may readily be recovered from thegases, whereas lower boiling constituents which are first removed fromthe tar in the vapor box 49 and separately collected in the clean oilreceiver 52 could be separated from the gases only with difliculty,especially where oils of low boiling range were present, owing to thenecessity for cooling the gases to much lower temperatures than requiredif only the heavy oils are present.

The pitch produced by distillation of this heavy tar is withdrawn thruthe levelling arm 33 into the mixing tank 34. It may be blended with taraind also clean oil if desired and disposed of as des red.

Clean oils of lowest boiling range are collected in the tank 52; oils ofhigher boiling range are collected in the tank 53; and oils of highboiling range are collected in the tank 47. These are all clean oildistillates. The lower boiling distillate or the two lower boilingdistillates may be extracted for tar acids. The distillate may beextracted by any of the usual methods of extracting tar acids from coaltar distillate. A ten percent solution of caustic soda or other suitablealkaline aqueous solution may be employed. The resulting neutral oil maybe blended with higher boiling distillate and this combined clean oilproduct may be blended with tar recovered directly from the hot cokeoven gases, as, for example, tarry oil from the tank 15 or heavy tarfrom the tank'l3 to produce creosoting composition. Clean distillate oilmay be used directly for creosoting composition without first beingextracted to remove tar acids, as, for example, where a singledistillate fraction of relatively low tar acid content is produced. Theclean oils are low in naphthalene. The process of blending to producecoal tar solution is dependent upon the product desired. Where a productof low naphthalene content is desired, heavy tar from the collector mainmay be preferred to tarry oil from the condensers as a blendingmaterial."

The three clean oil products may be blended and used for creosoting orone or two of the lowei' boiling fractions may be first extracted fortar acids and the remaining neutral oil may be blended with the higherboiling distillate to produce clean creosote oil.

Where clean oil is extracted to remove tar acids for tar acid recovery,the remaining neutral oil may be blended with the other tar and pitchingredients in the mixing tank 34 and burned as fuel. It may be fed tothe mixing tank thru the pipe 54.

By keeping the vapor chamber 49 under a vacuum a larger percentage ofoils will distill from the tar in the vapor chamber than when thedistillation is carried out under atmospheric pressure. The vacuum pumpmay advantageously be connected to the drain between the condenser 51.md the storage tank 52. When the vapor chambar is operated under avacuum, the line 26 is preferably connected with the pitch receiverrather than directly with the draw-off from the vapor chamber 49. Thepitch receiver and the distillate storage receiver 52 may advantageouslybe connected with the vapor chamber 49 and the condenser 51,respectively, thru barometric columns. By operating the vacuum chamberunder a vacuum, a larger percentage of ineluding higher boiling oils maybe distilled from the tar heated in the coil 46 in the condenser 41, orthe same quantity of lower boiling oils may be distilled in the vaporchamber with less preheating in the coil 46.

Although the invention has been described more particularly as appliedto the treatment of hot coke oven gases, it comprises the treatment ofother hot coal distillation gases. The gases are fractionally cooled toproduce a heavy tar and a lighter tar or tarry 'oil. The heavy tar isdistilled to pitch. The pitch produced may be blended with tar for fuel,etc. and the clean distillate oils may be variously used, as for thepreparation of tar acids or creosoting composition or clean creosoteoil, etc.

This application is in part a continuation of my copending applicationSerial No. 316,894, filed November 3, 1928.

I claim:

1. The method of producing a heavy tar and treating the same, whichcomprises collecting the coal distillation gases from a plurality of thecoke ovens of a coke oven plant in a gas-collector main, cooling thesegases to separate a heavy tar, separately collecting the heavy tar anddistilling it in two stages, the second stage comprising bringing theresidue from the first stage into direct contact with hot coke ovengases from the plant and the first stage comprising bringing the tarinto indirect contact with hot gases and vapors resulting from thesecond stage of the distillation and then flashing the heated tar.

2. The method of producing a heavy tar and treating the same, whichcomprises collecting the coal distillation gases from a plurality of thecoke ovens of a coke oven plant in a gas-collector main, cooling thesegases to separate a heavy tar, separately collecting the heavy tar anddistilling it in two stages, the second stage comprising bringing theresidue from the first stage into direct contact with hot coke ovengases from the plant and the first stage comprising heating the tar byindirect contact with hot gases and vapors resulting from the secondstage and flashing vapors from the heated tar in a vapor box maintainedunder a vacuum.

3. The method of producing a heavy tar and treating the same, whichcomprises collecting the coal distillation gases from a plurality of thecoke ovens of a coke oven plant in a gas-collector main, partly coolingthese gases to separate a heavy tar, separately collecting it,distilling the heavy tar to high melting point pitch, and obtaining twoclean oil distillate fractions, extracting the lower boiling fraction toobtain tar acids, and blending the resulting neutral oil with the higherboiling clean oil fraction.

4. In connection with a coke oven battery, a gas collector main, meansfor cooling the gases in the main to produce a heavy tar, a condensingsystem for cooling the resulting gases to separate tarry oil therefrom,receivers connected with the collector main and condensing system forthe heavy tar and the tarry oil respectively, a still, means forconveying hot gases from selected ovens to the still, the only feedingmeans to the still being a pipe for conveying the heavy tar from theheavy tar receiver to the still, an agitator within the stiil forspraying the tar up into the gases and thereby substantially detarringthe gases, and condensers for separating oils from the gases and vaporsleaving the still.

5. A coke oven plant, a gas collector main connected with the ovens ofthe plant, means for 6. In connection with a coke oven battery, a gascollector main, means for cooling the gases in the main to produce heavytar, a condenser for cooling the gases leaving the main tarry oil,separate receivers connected with the coliectormain andcondenserandtarryoilrespec STUART P RMELEE mm.

